<p>
  <mat-checkbox [formControl]="disableSelect">Disable select</mat-checkbox>
</p>
<p>
  <mat-form-field>
    <mat-select placeholder="Choose an option" [disabled]="disableSelect.value">
      <mat-option value="option1">Option 1</mat-option>
      <mat-option value="option2" disabled>Option 2 (disabled)</mat-option>
      <mat-option value="option3">Option 3</mat-option>
    </mat-select>
  </mat-form-field>
</p>
